[llvm] [llvm-mca][FeatureRequest] Itimeline graph, note source of delay for each instruction (PR #136423)

[Min-Yih Hsu via llvm-commits]

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@@ -156,6 +157,7 @@ class TimelineView : public InstructionView {
     static const char Dispatched = 'D';
     static const char Executed = 'E';
     static const char Retired = 'R';
+    static const char Pending = 'P';
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mshockwave wrote:

could you add some comments here and update the comment in the following line?

https://github.com/llvm/llvm-project/pull/136423